1. Field of the Invention
The present invention generally relates to a magnetic tape cartridge of a type having a protective lid assembly and, more particularly, to a mechanism in the magnetic tape cartridge for selectively opening and closing the protective lid assembly for exposing and concealing portion of a length of magnetic recording tape in relation to an in formation recording and/or reproducing head assembly.
2. Description of the Prior Art
The magnetic tape cartridge of the type referred to above includes, for example, an 8-mm video tape cartridge of a structure shown in FIG. 11. This illustrated magnetic tape cartridge comprises a casing 1 includes generally rectangular flat top and bottom panels, opposite side walls and front and rear walls, all of said side, front and rear walls being disposed between the top and bottom panels to keep them spaced apart a distance to define a tape chamber. The front wall is set back inwardly to define a generally U-shaped loading bay 6 in the casing 1 while leaving box arms on respective sides thereof that protrudes forwardly in a direction perpendicular to the longitudinal sense of the magnetic tape cartridge. Specifically, the loading bay 6 is delimited by inner side walls 7 of the respective box arms, that confront with each other, and the inwardly set-back front wall 8. This casing 1 accommodates therein a pair of reels to which opposite ends of a length of magnetic recording tape are anchored, respectively. A portion of the length of magnetic recording tape 2 drawn from one of the reels 3 and emerging outwardly from one of the box arms is adapted to travel towards the other of the box arms across the loading bay 6 and is then turned around the other of the reels.
The loading bay 6 is known as a space defined to permit various tape loading and unloading elements, forming parts of a tape loading and unloading mechanism in a magnetic recording and/or reproducing device with which the magnetic tape cartridge works, to be selectively inserted thereinto or withdrawn therefrom in response to loading or unloading of the tape magnetic tape cartridge. Specifically, when the magnetic tape cartridge is loaded in the magnetic tape player, that portion of the magnetic recording tape 2 traversing the loading bay 6 between the box arms is drawn out of the loading bay 6 and turned generally halfway around the rotary head-carrier cylinder in the tape player, but when the magnetic tape cartridge is to be removed from the tape player, that portion of the magnetic recording tape 2 is withdrawn into the loading bay 6.
While the magnetic tape cartridge is not in use, e.g., while the magnetic tape cartridge is not inserted into the magnetic tape player, that portion of the magnetic recording tape extending between the box arms across the loading bay 6 is protected by a transversely extending lid assembly which is generally comprised of front and rear lids 17 and 20 facing front and rear surfaces of the length of magnetic recording tape, respectively, the front and rear lids 17 and 20 are operatively linked together to move between open and closed positions as indicated by the phantom and solid lines in FIG. 11, respectively.
The inner side walls 7 of the respective box arms have respective guide grooves 40 defined therein in a mirror image fashion with each other for guiding the front and rear lids 17 and 20 in unison between the open and closed positions as is well known to those skilled in the art. Thus, movement of the double lid assembly from the closed position towards the open position allows that portion of the magnetic recording tape 2 to be exposed to the outside of the magnetic tape cartridge while movement of the double lid assembly from the open position towards the closed position allows that portion of the magnetic recording tape 2 to be concealed in a space between the front and rear lid 17 and 20 as shown.
In order for the magnetic tape cartridge to be accurately positioned relative to the head-carrier cylinder when it is loaded in the tape player, the casing 1 has a pair of positioning holes 9 each extending into a respective boss 11 through the bottom panel. Each boss 11 is substantially cylindrical in section and extends between the top and bottom panels of the casing 1 and is located generally at a junction between the front wall 8 and the associated side wall 7 of the box arm with a lateral portion 11a of the outer periphery of the boss 11 protruding into the loading bay 6. Protrusion of the lateral portion 11 a of the outer periphery of each of the cylindrical bosses 11 into the loading bay 6 is necessitated to secure, within a limited space inside the casing 1, a sufficient outer diameter of each boss 11 which is in turn necessitated to secure a required diameter of the respective positioning hole 9.
On the other hand, as part of the attempt to render the magnetic recording and/or reproducing system to be compact, attempts have been made to make the 8-mm video tape cartridge compact. To this end, it has been suggested, as disclosed in, for example, the Japanese Laid-open Patent Publication No 57, 210489, to use a triple lid assembly including, in addition to the front and rear lids, a top lid operatively linked with the front and rear lids to open an upper region above that portion of the magnetic recording tape 2 in response to movement of the front and rear lids towards the open position. The use of the top lid in combination with the front and rear lids makes it possible to increase the opening of the lid assembly while preserving a limited area of the loading bay.
A problem of interest would arise when attempt is made to employ mechanisms of the 8-mm video tape cartridge, in which the outer lateral portions of the cylindrical bosses necessarily protrude into the loading bay, in the magnetic tape cartridge of a type employing the triple lid assembly referred to above. In the magnetic tape cartridge designed to assist the system to be rendered compact, the area of the side wall 7 of each box arm is reduced and, therefore, protrusion of the outer lateral portions 11a of the respective cylindrical bosses 11 into the loading bay 6 often constitutes a cause of interference between left and right ends of the rear lid 20 and those outer lateral portions 11a of the respective bosses 11.
In order to substantially eliminate this problem, it may be envisaged to either reduce the width of the rear lid 20 as measured in a direction from one side wall to the other side wall of the casing, or relocate the guide grooves 40 for the rear lid 20 to a position further away from the front wall 8. It has, however, been found that reduction in width of the rear lid 20 may result in formation of a gap between each side wall 7 and the adjacent end of the rear lid 20 through which dust may deposit on that portion of the magnetic recording tape, whereas relocation of the guide grooves 40 requires an increase of the area of each side wall 7 facing the loading bay 6 and does therefore bring about a result contrary to the attempt to make the system compact.